| 초록 |
We have synthesized new blue polymer derivatives for light emitting diodes containing spirobifluorene and triphenyl amine with different ratio. Using Suzuki polymerization, we could get the high molecular weight and low PDI, Mw 130,000 ~ 50,000, PDI 1.5~2.2 respectively. These polymers are well soluble in common organic solvents such as THF, toluene, chloroform, which suggest making a good film morphology in spin casting process. These polymers were characterized with various methods, such as H1 NMR, CV, UV, PL, DSC, TGA. Resulting polymers show high Tg that suggests good thermal stability during the operation of the device. Polymer light emitting diodes were fabricated with the configuration of ITO/PEDOT:PSS/polymer/LiF/Ca/Al, which emitted deep blue color with maximum 451nm. Electroluminescence spectroscopy shows narrow emission width caused by the orthogonal structure of spirobifluorene causing the dilution effect to restrict interchain aggregation. Low turn on voltage, around 5 V, was achieved due to the presence of triphenyl amine suggesting easy hole injection from ITO to emitting layer. The maximum external quantum efficiency and luminescence were 1.2 cd / A ( at 13 V), 9,960 cd / m2 ( at 14 V) respectively. |
